Tube structure repair

ABSTRACT

A method and apparatus for repairing tubes that, during use, develop on the tube surfaces contaminating layers that prevent joining of new tube sections, as in fluid circulating heat transfer installations for chemical reactors. At least two surrounding protective sleeves are initially joined as by welding, to a tube at spaced locations on the tube to protect underlying portions of the tube from development of such layers. If a defect occurs between the sleeves, the defective tube may be removed by cutting through the sleeves and the tube underneath, removing the cut tube section, removing the remaining cut sleeve portions from the adjacent tube ends, and then joining a replacement tube section to the portions of the unremoved tube that were protected by the sleeves, preferably with new sleeves fixed in place over the resulting joints.

United States Patent 1 Pavilon 51 Feb. 20, 1973 [54] TUBE STRUCTURE REPAIR [75] Inventor: Stanley J. Pavilon, Shaker Heights,

[22] Filed: June 2, 1971 [21] Appl' No.: 149,213

Related U.S. Application Data [62] Division of Ser. No. 19,611, March 16, 1970, Pat.

[52] U.S. Cl. ..l65/75, 165/76, 165/134, 165/163, 138/113, 285/45, 285/286 [51] Int. Cl ..F28d l/06 [58] Field of Search ..29/47l.l, 479; 165/75, 76, 165/134; 285/45, 286, 15; 138/113, 114;

6/1970 Binford et al ..285/286 X 1/1971 Shaw et al. ....285/45 X Primary ExaminerCarroll B. Dority, Jr. Attorney-Bosworth, Sessions, Herrstrom & Cain [57] ABSTRACT A method and apparatus for repairing tubes that, during use, develop on the tube surfaces contaminating layers that prevent joining of new tube sections, as in fluid circulating heat transfer installations for chemical reactors. At least two surrounding protective sleeves are initially joined as by welding, to a tube at spaced locations on the tube to protect underlying portions of the tube from development of such layers. if a defect occurs between the sleeves, the defective tube may be removed by cutting through the sleeves and the tube underneath, removing the cut tube sec tion, removing the remaining cut sleeve portions from the adjacent tube ends, and then joining a replacement tube section to the portions of the unremoved tube that were protected by the sleeves, preferably with new sleeves fixed in place over the resulting joints.

9 Claims, 7 Drawing Figures PATENYTED FEB-201973 SHEET 1 0F 2 INVENTOR.

JrAm/za 1 MW; 04/

PATENTED FEB20 I975 3.717, 2 O 0 SHEET 2 OF 2 {5: 7 mvzzmox 5744/46) J. PAM/4 OA/ Bocumth, SHAW, fimd to'm K Chm 4 r raQA/EKS TUBE STRUCTURE REPAIR The present invention greatly reduces the above costs and difficulties and affords other advantages CROSS REFERENCE To RELATED APPLICATION hmmfme btamabl This application is a division of applicants US. 5 SUMMARY OFTHE INVENTION P applicatilon Sen 619,61 filed In apparatus of the invention the tube structure to be lgmand now located in an environment, as in a reactor chamber, BACKGROUND OF THE INVENTION where such an undesirable coating can occur is formed of at least one length of tube, usually connected to This invention relates to the repair of tubes and more supply and return manifolds, having at least two protecparticularly to the repair of a defective tube where, because of conditions to which the outer tube surface is sleeves lomed as by weldmg to the tube at Spaced exposed in Service the tube has become coated with an locations on it. Each sleeve surrounds and is preferably external contaminating layer h i not bl of radially spaced from the tube, and the opposite ends of being joined, as by a fusion process such as welding, each sleeve are joined, preferably by frusto-conical without extensive surface preparation to remove the -ti n to the xterior urf ce f th tube, o that the y t portion of the exterior surface of the tube beneath the Suck? j are Often chemlcal reacPors P sleeve is completely sealed by the fluid-impervious mg i f beds col 1tammg reactanis and If desired sleeve and its fluid impervious joints to the tube from finely divided catalytic agents. Certain types of reactions performed in such equipment require heat transfer means to maintain the desired reaction temperature. For this purpose heat transfer fluid is usually circulated through tubes arranged in the reactor tube length chamber in sinuous or coiled sections, usually welded This Structure P' repair of a defective Section of to Supply d r t ma ifold t fo m e bli Oftube between two sleeves without disassembly of the ten, layers or bundles of these assemblies are closely arreactor vessel and removal of an entire bundle or as ranged in stacked relation in the reaction chamber. bl f bi th fr The repait may be accom- In some services the reactants in the reactor chamber phshed in the reactor chamher according to react with the metallic outer surfaces of the tubes, so method f the invention described below F tubes become coated f j i that makes it According to the method of the invention, a tube impossible to weld or otherwise fusionoin metal to the structure of the type described above Comprising two outer surface of the tube metal without removing the coating. One particularly detrimental type of such reacprotective sieeves "owed ove r tube surface Pomons tion at the tube surface that occurs in certain services is betweetn Sleeves there a mbe defcct Such as a nitriding, wherein the metal tubing becomes corroded leak repalred by first makmg a transverse cut with a hat-d, brittle coating f an iron nitride that between the ends of each sleeve that are joined to the prevents welding or other fusion joining. If it should be 40 tube, th ough both the Sleeve and the tube, and the cut attempted to remove such coating to provide clean section of tube containing the defect is removed from metal for Welding other fusion j g, the tube the remainder of the tube. The sleeve portions on the would be so weakened at the cleaned portion as to lack remaining tube are then f bl cut away so as to sufficient strength or safety for service. Therefore If expose a length of protected reacted exterior Sup replafcemfmt of a damaged or i l tube face adjacent each cut end of the remaining tube. Then required it cannot be accomplished in a practical sense b ut the dama ed Section and weldin in a a replacement section is oined, as by a fusion oining y cu ing 0 g g such as welding, in place between the cut ends of the replacement section.

Therefore, in order to make tube repairs possible in f j tubfiusmg the clean Protected tube Surfaces in making the oints.

such apparatus it has been heretofore necessary to construct the reactor chamber of removable sections In a Preferred method, a new Sleeve is also installed demountably joined as by bolting at flanges, to permit over each of the two new joints, as by welding, to rosubstantial disassembly of the reactor, removal of one vide continued protection of the underlying unreacted more entire tube assemblies containing a defect, surfaces of the tube at these locations to make possible discarding of the entire assembly containing the defect, repair f future d f between such locations,

and replacement of the entire assembly containing the defect with a new assembly. Such a new assembly can BRIEF R PT ON OF THE DRAWINGS be very costly; in large reactors Such an assembly may FIG. 1 is an elevational view of a reactor with parts cost thousands of dollars. In such case an entire bundle of tubing including supply and return manifolds must broken f f and Show" m f 9 reveal bundles of usually be removed, disassembled, reassembled, with tubes within the reactor for circulating a heat transfer the new assembly in place, and replaced when repair is fluld;

required, even if only a single tube is defective. This 2 1S a Perspectwe Showmg one layer or procedure is cumbersome, time-consuming, and adds sembly ofthe tube bundleiand to initial cost of the reactor as well as to the cost of F GS- 3 to 7 are elevational views with parts broken repairs by use of a costly complete replacement asaway and shown in section to illustrate sequentially the sembly. method of the invention.

the surrounding environment and thus protected from reaction or corrosion; when exposed it can be readily welded or otherwise fusion-joined to a replacement DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings, FIG. 1 shows an apparatus in which the invention may be advantageously used, for producing a gaseous chemical product by a fluidized bed process. The apparatus of FIG. 1 includes a reactor 1 comprising a shell 2 made up of upper and lower sections 3 and 4 welded to an intermediate section 5 at seams 6 to provide a fluid-tight joint at the pressures used. Because of the invention, it is not necessary to utilizeconventional construction comprising shell parts that are bolted together, and thus possibilities of leakage at the joints is eliminated.

The shell 2 defines a reactor chamber 7, having at its bottom spaced conduits 8, 9 for introducing a gaseous reactant, and having one or more horizontal conduits 12 for introducing another fluid reactant. The shell 2 also has at its top a conduit 13 through which the gaseous reaction product is discharged.

Finely divided fresh catalyst is introduced through inlet conduit 14 and spent catalyst is discharged through outlet conduit 15. In the chamber 7 catalyst particles are suspended in a fluidized bed by the fluid reactants and gaseous reaction product. The techniques for maintaining such a bed and carrying out the reaction are known, and form no part of the invention.

A manway 16, provided with a removable cover 17, is provided at the top of the reactor to permit access for assembly of or repair of internal parts in chamber 7. According to the invention, repairs may be made to the below described tubes within the reactor chamber without taking the reactor shell apart. Another manway 27 is located the side of the reactor.

Located within the reactor chamber 7 is a tube structure 20 or group of tube assemblies for circulating a heat transfer fluid to maintain a desired temperature for the particular reaction. The reaction for example, may be endothermic so that the heat transfer fluid must be a heating fluid to maintain the desired reaction. Molten salt for example may be used as the heat transfer fluid in some cases.

The tube structure 20 includes vertical inlet pipes or risers 21 and also vertical outlet pipes or risers 22 which as indicated in FIG. 1 extend from opposite sides of the reactor chamber 7 to riser access ports 23 and 24 respectively. The access ports 23 and 24 are sealed when the reactor 1 is in use. The risers 21 and 22 are connected to fluid supply means including pumps (not shown).

Each inlet riser 21 is connected to one of the inlet manifolds 25 and each outlet riser 22 is connected to one of the outlet manifolds 26. Each riser 21 and 22 has a protective sleeve 29 which is welded at its ends to the surface of its riser adjacent the lower end of the riser. The sleeves 29 permit cutting and rewelding, so that the ends of the risers may be separated from and reconnected to manifolds 25 or 26 when repairs are to be made according to the method of the invention as described below.

Each opposite pair of inlet and outlet manifolds 25 and 26 is associated with a tube assembly or layer (FIG. 2) of which six are shown, one of which, identified by the number 30, illustrated in perspective in FIG. 2. Each layer comprises a plurality of tube sections 31 which in the embodiment shown are of sinuous form so as to make three passes back and forth between the opposite manifolds 25 and 26. Each tube section 31 is connected at one end by a welded butt joint 36 to a tubular stub 32 extending from supply manifold 25, and at its other end to another stub 33 extending from outlet manifold 26.

In accordance with the invention, two sleeves 35 are positioned over the joints between the tube section 31 and the stubs 32 and 33 so as to cover substantial portions of the surfaces at the adjoining ends of the tubular stubs and the section 31. The opposite ends of each sleeve 35 are welded to the surfaces of the respective tubular stubs and the tube section, as indicated by numerals 37 and 38 shown in FIG. 3, to provide a tight seal. With this arrangement the surface portions at the ends of each stub 32 or 33 and the adjoining tube section and are protected from the action of reactants in thereaction chamber 7. Such reactants in some services react with the metal on the surface of the tubing to form a coating that makes welding impossible and that if removed by grinding or otherwise harmfully weakens the metal. Preferably, each sleeve 35 has tapered, preferably frusto-conical ends 35 that decrease in size to the tube from a larger major portion of the sleeve, the inner diameter of the major portion of each sleeve being sufficiently greater than the outer diameter of the tube so that a protected annular space is defined within each sleeve 35 between its inner surface and the tubing and so that the metal under the sleeve is completely protected against formation of the above indicated coating. The annular space also prevents undesired stresses between the sleeve and tube, and the tapered ends aid in this and also make it easier to remove the sleeve from the tube when desired.

REPAIR PROCEDURE For the purpose of disclosing a typical repair procedure in accordance with the method of the invention, it will be assumed that a defect occurs in one of the tube sections 31 of the layer 30. Referring to FIG. 1 it will be seen that the assembly or layer 30 is the fourth layer down from the top of the six layers of the illustrated tube structure 20. Accordingly, in order to permit access for a repairman, the three layers of tube sections above the layer 30 must be raised sufficiently to provide working space for the repair operation. To accomplish this the inlet and outlet risers for the three layers above the layer 30 are cut free from their respective inlet and outlet manifolds 25 and 26 by cutting through the riser sleeves 29. If desired, the cut risers 29 may be removed through the respective riser access ways 23 and 24 or else may be merely raised high enough to provide sufficient overhead clearance.

When this is done the three assemblies or layers above the layer 30 may be raised up at one end or both ends sufficiently to permit access to layer 30 for repair. Then a repairman may enter through the manway 27.

Repair of a defective tube section 31 can then be undertaken. According to the invention (FIGS. 3-7) the defective section 31 is cut free of the layer 30 by making a transverse cut through the central portion of each of its sleeves 35 and through the underlying tube. Once the cut is completed the defective tube section is removed through the manway 27. The result is apparent from FIG. 4, which shows a portion of the tubular stub 33 carrying the remaining portion of cut sleeve 35. In this case the cut was made through the tubular stub at a location closely adjacent the initial weld joint so that the old weld metal is removed with the defective tube section.

Thereafter, the severed sleeve portion that remains on the tubular stub'33 is cut away to leave only a scrap ring 39 formed of the remainder of end portion 35' of the sleeve, as indicated in FIG. 5. This exposes essentially all the protected portion of the tubular stub 33 which, because it was protected from the reactants in the reactor chamber, has its outer surface clean and free of any reaction product or coating that formed on unprotected surfaces of the tube. The ring 35 is then preferably largely if not entirely removed, as by grinding, to remove any metal or corners that could cause undesired thermal stressing or cracking of the tube. The stub 32 from which the other end of defective section 31 was cut is similarly treated.

At this time, a replacement tube section 40 is introduced into reactor'chamber 7 through the manway 27 and is suitably positioned with its opposite ends abutting the ends of the tubular stubs 32 and 33. These abutting ends are then fully welded as indicated at 41 (FIG. 6) to place them in proper alignment and form a tight joint between the old and replacement sections of the tube. I

According to the preferred practice of the invention new sleeves 42 will have been placed on the replacement section 40 before the new section is positioned and welded, and after the welding is completed each new sleeve 42 is moved from its initial position illustrated by FIG. 6 over its associated tube joint 41 to its final position illustrated by FIG. 7. The ends of the sleeve are then welded by a full fluid-impervious weld to the underlying outer clean surfaces of tubing end portions, as illustrated by the numerals 43 and 44 (FIG. 7) thus completing the repair. It will be noted that each replacement sleeve 42 is positioned slightly inward of the position taken initially by the end 35' of the original sleeve 35 indicated in broken lines 35" in FIG. 7, to space the location of the weld 41 from any prior weld metal from the old sleeve 35 and insure that the new sleeve will be welded to clean, protected metal on the old tube portion. Several subsequent replacements for the same tube section can be made according to this procedure, probably many more than would ever be required during the life of the reactor.

After the repair is completed the raised layers above the layer 30 are sequentially lowered into their proper places and their respective risers 21 and 22 are rewelded with new sleeves 29 thereon according to the same general procedure described above with respect to the replacement of a tube section. The replacement riser sleeves 29 will preferably be shorter than the original sleeves because of the shorter surface area available for welding. Once the layers have all been relocated and their respective risers welded in place the reactor will be ready for use.

While the invention has been illustrated and described with respect to specific embodiments of the apparatus and method thereof it will be understood that variations and modifications may be made in the form and arrangement of the several parts and elements thereof and in the repair procedure without departing from the spirit of the invention. The invention therefore is not to be limited to the particular structure and procedure herein shown and described nor in any manner that is inconsistent with the extent to which the progress in the art has been advanced by the invention.

I claim:

1. A reactor vessel comprising a closed reaction chamber; and a tube structure located within said chamber for circulating a heat transfer medium therethrough and comprising a plurality of superposed layers of tube, an inlet manifold and an outlet manifold for each layer, a plurality of tube sections connected between said manifolds, and a pair of sleeves of fusionjoinable material positioned around each tube section, one adjacent each respective manifold, each sleeve being fusion-joined at spaced locations thereon to the exterior surfaces of said tube section and of a tube portion connected to one of said manifolds by spaced fluid-impervious joints on said tube section and tube portion whereby the exterior surface portion of said tube section and the tube portion covered by each sleeve is sealed from the reaction chamber.

2. The apparatus of claim 1 in which each of said sleeves is radially spaced from said tube section and tube portion between said fused joints.

3. The vessel of claim 1 including a manway formed in the sidewall of said vessel and adapted to be used for moving a tube section to or from any one of said layers into and out of said reaction chamber.

4. The vessel of claim 1 wherein each of said manifolds has a tube connected thereto that extends through said vessel for circulating fluid to and from said layers and wherein each tube has a sleeve fusion-joined at spaced locations thereon closely adjacent its respective manifold to seal the exterior surface of said tube covered by said sleeve from the reaction chamber.

. 5. The apparatus of claim 1 in which said tube section and tube portions are formed of metal, and said sleeves are formed of metal and are fusion-joined to the exterior surface of said tube section and tube portions by spaced fluid-impervious fused metal joints.

6. A reactor vessel comprising a closed reaction chamber; and a tube structure located within said chamber for circulating a heat transfer medium therethrough and comprising an inlet conduit, and outlet conduit, a tube section connected between said conduits, and a pair of sleeves of fusion-joinable material positioned around said tube section, each sleeve being fusion-joined at spaced locations thereon to the exterior surfaces of said tube section and of a tube portion connected to one of said conduits by spaced fluid-impervious joints on said tube section and tube portion whereby the exterior surface portion of said tube section and the tube portion covered by each sleeve is sealed from the reaction chamber.

7. The apparatus of claim 6 in which each of said sleeves is radially spaced from said tube section and tube portion between said fused joints.

8. The apparatus of claim 6 is which said tube section and tube portions are formed of metal, and said sleeves are formed of metal and are fusion-joined to the exterior surface of said tube section and tube portions by spaced fluid-impervious fused metal joints.

9. The apparatus of claim 4, in which each of said sleeves is radially spaced from said tube between said fused joints. 

1. A reactor vessel comprising a closed reaction chamber; and a tube structure located within said chamber for circulating a heat transfer medium therethrough and comprising a plurality of superposed layers of tube, an inlet manifold and an outlet manifold for each layer, a plurality of tube sections connected between said manifolds, and a pair of sleeves of fusion-joinable material positioned around each tube section, one adjacent each respective manifold, each sleeve being fusion-joined at spaced locations thereon to the exterior surfaces of said tube section and of a tube portion connected to one of said manifolds by spaced fluid-impervious joints on said tube section and tube portion whereby the exterior surface portion of said tube section and the tube portion covered by each sleeve is sealed from the reaction chamber.
 1. A reactor vessel comprising a closed reaction chamber; and a tube structure located within said chamber for circulating a heat transfer medium therethrough and comprising a plurality of superposed layers of tube, an inlet manifold and an outlet manifold for each layer, a plurality of tube sections connected between said manifolds, and a pair of sleeves of fusion-joinable material positioned around each tube section, one adjacent each respective manifold, each sleeve being fusion-joined at spaced locations thereon to the exterior surfaces of said tube section and of a tube portion connected to one of said manifolds by spaced fluid-impervious joints on said tube section and tube portion whereby the exterior surface portion of said tube section and the tube portion covered by each sleeve is sealed from the reaction chamber.
 2. The apparatus of claim 1 in which each of said sleeves is radially spaced from said tube section and tube portion between said fused joints.
 3. The vessel of claim 1 including a manway formed in the sidewall of said vessel and adapted to be used for moving a tube section to or from any one of said layers into and out of said reaction chamber.
 4. The vessel of claim 1 wherein each of said manifolds has a tube connected thereto that extends through said vessel for circulating fluid to and from said layers and wherein each tube has a sleeve fusion-joined at spaced locations thereon closely adjacent its respective manifold to seal the exterior surface of said tube covered by said sleeve from the reaction chamber.
 5. The apparatus of claim 1 in which said tube section and tube portions are formed of metal, and said sleeves are formed of metal and are fusion-joined to the exterior surface of said tube section and tube portions by spaced fluid-impervious fused metal joints.
 6. A reactor vessel comprising a closed reaction chamber; and a tube structure located within said chamber for circulating a heat transfer medium therethrough and comprising an inlet conduit, and outlet conduit, a tube section Connected between said conduits, and a pair of sleeves of fusion-joinable material positioned around said tube section, each sleeve being fusion-joined at spaced locations thereon to the exterior surfaces of said tube section and of a tube portion connected to one of said conduits by spaced fluid-impervious joints on said tube section and tube portion whereby the exterior surface portion of said tube section and the tube portion covered by each sleeve is sealed from the reaction chamber.
 7. The apparatus of claim 6 in which each of said sleeves is radially spaced from said tube section and tube portion between said fused joints.
 9. The apparatus of claim 4, in which each of said sleeves is radially spaced from said tube between said fused joints. 